1. Field of the Invention
This invention relates to antennas for use with radio transceivers. More particularly, the invention provides a small multiband patch antenna with very high efficiency and high isolation for use in cellular telephones and other personal electronic devices.
2. Background
Cellular telephones and other wireless electronic devices are widely used. Such devices have steadily grown smaller with advances in miniaturization of electronic components. This has created a challenge for the design of antennas in such devices. At the same time, it is desirable for the antenna to have a broad working bandwidth.
Various methods are known in the art to broaden the operating bandwidth of an antenna. Most of these employ parasitic elements that are excited by a driven element. In most cases, the elements are capacitively coupled. In the case of patch elements, the methods often rely on optimization of the coupling between the patches. The modes excited inside the different elements are basically the same.
Different methods exist in order to reduce the dimensions of a patch antenna. One such method is described in Size Reduction of Patch Antenna by Means of Inductive Slits, Reed, S., Desclos, L., Terret, C., Toutain, S., APS/URSI 20000 Utah. This method places a set of slits in the patch that represents an inductive loading. The authors report that a reduction of 50% in the dimensions of the patch antenna was achieved with this approach. Generally speaking, however, as the patch gets smaller, the efficiency decreases and the working bandwidth gets smaller.